Objective To investigate the forms of water iodine in areas with excessive iodine in water of Henan Province.Methods From December 2013 to January 2014,50 water plants in 4 cities (Puyang,Xinxiang,Kaifeng and Shangqiu cities) of Henan Province were selected from the areas with excessive iodine in water where iodized salt and centralized water supply were stopped for more than 5 years.In each selected water plant,3 water samples were collected.I2-Starch Spectrophotometer was used to measure the iodine content and identify the forms of iodine in water samples.Results A total of 403 water samples were collected and ultimately 286 samples met the requirement (water iodine ≥ 80 μg/L).Among the 286 samples,iodine existed in the forms of iodide in 6 water samples,of both iodate and iodide in 139 water samples,and of iodate in 141 water samples.In water samples with iodine content lower than 150 μg/L,the proportions of forms of iodide and both iodate and iodide,were 26.67％ (12/45) and 73.33％ (33/45),respectively.In water samples with iodine content between 150-299 μg/L,the proportions of the forms of iodide,both iodate and iodide,and iodate,were 4.88％ (6/123),79.67％ (98/123) and 24.39％ (30/123),respectively.In water samples with iodine content higher than 300 μg/L,the proportions of the forms of iodide and both iodate and iodide,were 18.18％ (2/11) and 81.81％ (9/11),respectively.Conclusions In areas with excessive water iodine in Henan Province,iodine mainly exists in the forms of iodate,or both iodate and iodide.No sample is found to contain periodate.

Objective To understand the stability of iodine content in potassium iodide iodized salt and potassium iodate iodized salt during production.Methods The sodium sulfate type brine well rock salt and calcium salt brine well rock salt as raw material were used to produce potassium iodide salt and potassium iodate salt by different iodization methods of before and after fluid bed dryer and then the loss of iodine during production was measured,meanwhile iodine content of powder salt was determined.According to the "Belt Delivery Sampling of Sampling Methods of the Main Products in the Salt Industry" (GB/T 8616-2001),25 standard salt samples and 6-24 powder salt samples were collected in the same batch.The salt iodine content was determined by oxidationreduction titration and direct titration of the "General Test Method in Salt Industry-Determination of Iodine" (GB/T 13025.7-2012).Results For the sodium sulfate type brine well rock salt,there was no statistical difference in iodine loss rate between potassium iodide salt and potassium iodate salt (16.55％ vs.19.60％,x2 =0.01,P ＞ 0.05) by iodization of before fluid bed dryer.The iodine loss rate of potassium iodide salt was 2.17％ and the iodine loss of potassium iodate salt was undetectable and there was no statistical difference between the two (x2 =2.19,P ＞ 0.05)by iodization of after fluid bed dryer.For calcium salt brine well rock salt,the iodine loss rate of potassium iodide was less than that of potassium iodate (20.60％ vs.39.75％,x2 =8.70,P ＜ 0.05) by iodization of before fluid bed dryer and neither of them was lost by iodization of after fluid bed dryer.Conclusions For both sodium sulfate type brine well rock salt and calcium salt brine well rock salt,the iodine loss of iodide iodized salt is not higher than that of potassium iodate during iodization of before or after fluid bed dryer.Since the iodine loss during iodization of before fluid bed dryer is significantly higher than that after fluid bed dryer,adopting iodization of after fluid bed dryer to produce iodized salt should be recommended.